The behavioural phenotype of Smith-Magenis syndrome: evidence for a gene-environment interaction

Behaviour problems and a preference for adult contact are reported to be prominent in the phenotype of Smith-Magenis syndrome. In this study we examined the relationship between social interactions and self-injurious and aggressive/disruptive behaviour in Smith-Magenis syndrome to explore potential operant reinforcement of problem behaviours and thus a gene-environment interaction.

Observational data on five children with Smith-Magenis syndrome (age range 3 to 13 years) were collected for between 9 and 12 h. The associations between purported phenotypic behaviours and two environmental events (adult attention and demands) were examined using descriptive analysis.

All participants engaged in self-injurious behaviour and aggressive/disruptive outbursts. Sequential analyses of aggressive/disruptive outbursts and self-injury revealed that these behaviours were evoked by low levels of adult attention and led to increased levels of attention following the behaviours in three and two participants respectively out of the four for whom this analysis was possible.

Problem behaviour in Smith-Magenis syndrome was evoked by decreased social contact in three out of four children. These data, considered alongside the preference for adult contact and the significantly increased prevalence of these behaviours in Smith-Magenis syndrome, illustrate a potential gene-environment interaction for problem behaviour in this syndrome.